Electrolytic pickling apparatus



June 30, 1936. A. E. CHESTER 2,045,581

ELECTROLYTIC PICKLING APPARATUS Filed Oct. is, 1933 2 Sheets-Sheet 1 mNvEkTOR ATTORNEY June 30, 1936. A. E. CHESTER ELECTROLYTIC PICKLINGAPPARATUS Filed Oct. 18, 1953 2 Sheets-Sheet 2 ATTORNEY Patented June30, 1936 UNITED STATES ELECTROLYTIC PICKLING APPARATUS Allan E. Chester,Brooklyn, N. Y., 'assignor, by direct and mesne assignments, to FerroEnamel Corporation, Cleveland, Ohio, a corporation of Ohio ApplicationOctober 18, 1933, Serial No. 694,028

2 Claims. 31. 204-5) The present invention relates to the cleaning andpickling of iron and steel generally including, for example, high carbonsteel, low carbon steel, such, for example, as enamellerssteel, alloy 5steel and iron, wrought iron, cast' iron, cast'steel, malleable iron,semi-steel, and drop forgings of various compositions.

An object of the invention is to provide an improved pickling bath whichaccomplishes the pickling operation in less time than is required by thebaths now commonly in use and at the same time inhibits attack by thebath on the base metal itself, in contradistinction to hitherto knownbaths employing an inhibitor which slows the action of the bath.

. Another object of the invention is to provide an electric picklingsystem that isneither impractical nor too costly to be used by steelmanufacturers and fabricators, the system being one capable of handlinglarge quantities of work, for example, quantities as large as are atpresent cleansed in non-electric pickling systems, as distinguished fromprior proposed electric pickling systems that have been eitherimpractical or too costly for the pickling of large quantities of workcommercially.

Another object of the invention is the provision of an electric picklingsystem in which the abovementioned improved pickling bath is used as anelectrolyte, the present process providing an electrolyte of greaterchemical efficiency than the prior known pickling baths and having theadvantages of producing electrically the evolution of gas in'largequantities and causing ionization of the electrolyte which results in agreater flow of ferric, ferrous, and other ions from the work I andconsequently in a higher combined chemical and electrical eiiiciency. I

Another object of the invention is the provision 40 of a method andapparatus for employing alternating current in an electrolytic picklingcell whereby the work to be cleansed is automatically brought intocontact with the electrical circuit without external or internalracking, clamping 45 or connecting individual pieces of work in thecircuit.

Another object of the invention is the provision of anelectricpicklingsystem which utilizes, low current densities to facilitate theremoval of 50 oxides including magnetic oxides. By low current densitiesis meant current densities of the order of 1 to 15 .amperes per squarefoot of work surface, as distinguished, for example, from relativelyhigh current densities of 50 or more am- 5 'peres per square .foot' ofwork surface.

Other objects of the invention include the provision of an electricpickling system in which the circuit is complete at all times, includingpermanent electrodes in the cell, the word com-f plete as here usedhaving reference to the presence at all times of all necessary parts ofthe circuit for functioning, whether the circuit be open or closed, theplacing of the work in the bath merely bringing it in physical andelectrical contact with a permanent electrode already present in thebath, there being no necessity for using the work itself as eitherelectrode and there being therefore no necessity for clamping orotherwise attaching or securing the workin the electric circuit; and toprovide such a system in which the work, in large quantities ifpreferred, may be placed in a suitable metal basket or container, whichis then merely placed in the bath to rest upon an electrode provided toreceive it, the container and all the individual pieces of work thereinbeing thus included-in the electric circuit by the mere act ofdepositing the work in the bath. I

Further objects are the provision of a novel pickling systemaccomplishing the foregoing obtem in which additional or externalheating ap-. paratus orheating energy, such as steam, are frequently notrequired. For example, in many cases the operation may be started withthe bath at room temperature the temperature of the bath rising as thepickling process continues,

.and in which the process of the present invention may be efficientlycarried out.

In the drawings: i

Fig. 1 is a perspective view of i a pickling tank embodyingconstructional features of the invention; 1 A

Fig. 2 is a top plan view of the tank of Fig. 1 on a reduced scale;

Fig. 3 is. a side elevation showing one form 25 jects and advantages atlow cost in actual comv mercial pickling practice; and to provide asysof work-holding basket in the tank of Fig. 1, and

Fig. 4 is an end view of said basket.

Referring to the composition of pickling baths prepared in accordancewith the invention, the amount of water used depends, of course, on thesize of the tank, and in commercial installations may vary, for example,from gallons to 5,000 gallons and more.

The amount of sulphuric acid may vary widely with reference to theamount of water and may be present in amounts from of 1% to 15% byweight of water in the bath.

In accordance with the present invention, an ingredient is added to suchbaths as the foregoing, the added ingredient being d-gluconic acid, asubstance having apparently contradictory properties in that itfunctions in the bath not only as an inhibitor, but also as astimulator.

The following is an example of pickling bath made up in accordance withthe invention:

Water 100 parts by weight Sulphuric acid 3 to 10 parts by weightd-gluconic acid part to 10 parts by weight The sulphuric acid used may,for example, be 66 B. commercial sulphuric acid.

The d-gluconic acid used is preferably that obtained by oxidizingcommercial glucose, the latter consisting of maltose, dextrose anddextrine. The d-gluconic acid as used in the above formula is a 50%solution. The term d-gluconic acid in the claims is meant to coverd-gluconic acid whether solely or as the d-gluconic acid in (d+l)-g1uconic acid.

In addition to the foregoing ingredients, other substances may, ifdesired, be included in the bath. For example, a wetting agent such aslicorice may be used in amounts varying from 1/25 of 1% to 1% by weightof total acid used. Also, isopropyl alcohol or a sulphonated fattyalcohol may be used in amounts varying from 1% to 25% by volume of waterused. The alcohol aids in removing certain insoluble soap micelles, suchas insoluble calcium and magnesium soap micelles, from the pores ofsteel, apt to be present therein after the steel has been cleaned in analkaline bath and prior to the pickling operation.

The bath given in the foregoing example may be used in the presentpickling process at a temperature varying from F. to 180 F., and hasbeen found suitable for pickling high and low carbon steel wire, such asnickel-chromium alloy wire annealed and normalized, the current being 60cycle A. 0., current density varying from 1 ampere per square foot ofwork surface to 10 amperes per square foot of work surface.

Pickling baths prepared as above have also demonstrated greatlyincreased efficiency in the pickling of low carbon enamellers steel, thetemperature range being from 90 F. to F. and the current density varyingfrom 0.25 ampere to 10 amperes per square foot of work surface.

The d-gluconic acid present in the bath prevents the formation of ironoxide slime on the work. It also assists in wetting the surface of thesteel to be pickled. It is in itself an effective solvent for the loweroxides of iron, and, finally,

it serves not only as an inhibitor, but also stimulates to a greatextent the attack of the pickling solution upon the sub-oxides of iron.

Referring to the construction of the tank shown in the drawings, thetank may be rectangular, as indicated in Fig. 1, and provided with aninterior lining H of lead or wood. Extending longitudinally along oneside of the tank is a bus bar [3 to which a plurality of any suitableinert electrodes l5, l1, l9 and 2| are connecmd. As shown, theseelectrodes extend over the side of the tank and thence downwardlythereinto near the adjacent tank wall, these vertical portions beingpreferably enclosed by some, insulating materia1 23, such as bakelite.Each of these electrodes near the bottom of the tank is formed with ahorizontally extending work supporting portion 25. These work supportingportions are insulated from the tank lining by suitable supports ofinsulating material, such as Wooden 2 x 4s or 4 x 4s. These electrodesare referred to as permanent electrodes because they are notdisconnected or removed therefrom for successive pickling operations,but form a part of the construction of the electrolytic pickling cell,the word permanent not being intended to imply that the electrodes cannot under any circumstances be removed.

Cooperatingwith the work supporting electrodes I5, l1, l9 and 2| are aplurality of plate electrodes 21, 29, 3| and 33, which extend downwardlyinto the tank near the opposite side wall thereof, beingsupported in thetank at their bottom edges by any suitable form of wooden or othersupporting means, such as the wooden supports 35 shown in the drawings.The electrodes 21, 29, 3| and 33 are connected to a bus bar 39 extendinglongitudinally along the upper outside of their adjacent tank wall.

Steam pipes 4| may be provided for the purpose of heating the picklingelectrolyte when desired, which may be merely at the outset of thepickling operation or may be throughout the operation.

The tank is provided with a bottom outlet for draining and may, ofcourse, be provided with any suitable water inlet.

Large quantities of work may be pickled in accordance'with the presentinvention, for example, quantities as large as are at present ordinarilypickled at one time in the usual sulphuric acid pickling baths, withoutany electric current. For this purpose the basket shown in Figs. 3 and 4may be used, thebasket or baskets used being of a convenient size to fitin the tank efiiciently when containing work to be pickled and depositedin the tank to rest upon the horizontally extending portions 25 of thework supporting electrodes I 5, l1, l9 and 2|.

The bus bars are connected in an A. C. circuit in obvious manner, thecommonly used GO-cycle current being entirely suitable.

It will be understood that many variations may be made in the size andshape of the electrodes without departing from the invention; and itwill also be noted that the invention provides an electric picklingsystem in which onlyvery low current densities are required, so that,although providing for the pickling of large quantities of work, theexpense for current is relatively small and well overbalanced by veryconsiderable saving in time as well as saving of heating expense andincreased pickling efiiciency due not only to the may be simplydeposited in'the bath upon the electrodes, thus'becoming a part of thealternating current circuit through the basket or baskets, when sucharev used, and without requiring any external or internal racking,clamping or connecting of individual pieces of work in the circuit.

What is claimed is:-

1. Electrolytic pickling apparatus comprising in combination a picklingsolution tank. set of electrodes overlying the bottom of said tank andso arranged as to provide a supporting bed for a work basket, anotherset of electrodes extending into said tank along the wall thereof tobelow the normal liquid level therein, and an electrically conductivework basket adapted to rest on said first named electrodes. a

2. Electrolytic pickling apparatus comprising in combination a picklingsolution tank, a work 5 basket in which the work articles may be looselypiled, two sets of electrodes fixed in said tank below the normal liquidlevel therein and so arranged as to permit saidzwork basket to be freelymoved into and out of said tank without 10 disturbing said electrodesand one set of said electrodes s'o arranged as to provide a supportingbed for said work basket.

v ALLAN E. CHESTER.

